Separation of wax and asphalt from hydrocarbon oil



June 16, 1953 F. DENNIS ErAL SEPARATION OF WAX AND ,ASPHALT FROM HYDROCARBON OIL Filed Sept. 13, 1949 Patented June 16, 1953 vSEPARATION 0F WAX AND ASPHALT FROM HYDROCARBON OIL VFranklin L. Dennis, Clayton,r .and4 vWilliam H. King and Harold C. `Myers', Woodbury, N. J., assignors to SoconyV-VacuumkOil Company, Incorporated, a corporation of NewYork Application september-.13, 1949, kserial No. 115,444

s claims. (ol. 19a-17) This invention has to do with the separation of hydrocarbon `and hydrocarbon derivatives of diierent molecular configuration from mixtures containing the same.

I. FIELD. OF INVENTION Numerous processes have been developed from the separation of hydrocarbons and hydrocarbon derivatives of different `molecular,configuration by taking advantage of their selective solubility in selected reagents or solvents from which they may later be separated. Exemplary of hydrocarbon separation procedures is the Edeleanu procces's, wherein parainic materials are separated from aromatics by virtue of the greater solubility of aromatics in liquid sulfur dioxide. Lubricant oil solvent reiining processes, solvent deasphalting, solvent dewaxing and the like are further examples of the separation of hydrocarbons of different molecular conguration. Typical of selective solvent procedures for separating hydrocarbon derivatives is the Separation of paraflin wax, monochlorwax and polychlorwaxes,V with acetone as the selective solvent.

This invention is kconcerned with the general field outlined above, but based upon a different and little-knownphenomenon, namely the diiering ability of hydrocarbons and hydrocarbon derivatives to enter into and to be removed from certain crystalline complexes. As used herein, the term complexfbroadly denotes a combination of two or more compounds.

y 11. PRIORAR'I"v For some years it has been known that variousl isomers lof aromatic hydrocarbon ,derivatives form complexes withurea. 'Kremann (Monatshefte f.

Chemie 28 1125 (1907i) observed that complexes'L designated as double compounds, ofY urea and the isomeric cresols are stable at diierent temperatures."l Schotte and Briewe (1,830,859) latery separated meta-cresol from the correspondingy para isomer by selectively forming a meta-.cresolurea complex,` which was described as an addition compound; the latter compound was sepa-V rated from the para isomer `and thenV splitupby distillation or with water or acid to obtainpure'- meta-cresol.v The additioncompound oiy meta` cresol and urea was shown thereafter to have utility as a disinfectantA @ruwe-1,933,757). Bentleyand. Catlow (1,986,901) found a number of aromatic amines .containing at least onebasic amino group capable of.forr'ning double compounds with certain isomeric phenols. It has also been shown that trans-oestradiol can be separated fromthefcorresponding cis-compound by forming a diflicultly soluble compound of urea and trans-oestradiol (Priewe-2,300,134).

The` forces between urea and the compounds y of the foregoing complexes are due to specific chemicalinteraction between the various funcn tional groups.

; ditions--Produkt A with urea.

One heterocyclic compound, V21.6 lutidine, has been found to form ancrystalline compound with urea, thus affording a means of separating the lutidine from beta-V and gamma-picolines (Rie-V Comparatively few aliphatic hydrocarbon `de-l rivatives have been known to form complex com pounds with urea. In German patent application B 190,197, 1V d/ 12 (Technical lOil Mission, Reel 143; Library of Congress, May 22, 1946), Bengen described a method for the separation of aliphatic oxygen-containing compounds (acids, alcohols, aldehydes, esters and 'ketones) and of straight chain hydrocarbons of at least six carbon atoms from mixtures containing thersame, the method being predicated upon the ability'of such compounds and hydrocarbons to form ad- A mixture con,- taining such aliphatic compounds is vcontacted with a. concentrated solution of urea in water, methanol, or ethanol, and the like. In the Technical Oil Mission translation of the Bengen application, however, the urea complexes were designated adducts, which term apparently stems from the anglicized "addition product. The adducts are separated into theircomponents, urea and straight chain hydrocarbon-ori aliphatic oxygen-containing compound, by heating or by the addition of` methanol, water or anV aqueous solution.

Thiourea has also been known to form complexes, perhaps the Frst of which is a complex with ethyl oxalate` (Nencki, Berichte 7 780 (1874)). Recently, crystalline molecular coinplexes of thiourea and certain organic comy pounds, were described by Angla (Compt. rendus The organic com-- Crystalline molecular complexes of y such com-v pounds-aredissociated bywater and organic solvents to their components, thiourea and a compound of the foregoing type.

III. DEFINITIONS From the foregoing discussion of prior art (II), it will be clear that a variety of terms have been applied to urea and thiourea complexes. The latter have been rather loosely described as double compounds, addition compounds, dif cultly soluble compounds, Additions--Prcdukt, adducts, and crystalline molecular complexes. All of these terms are somewhat ambiguous in that they have also been used to describe products or complexes of different character than the urea complexes under consider, ation. This is particularly so with the term adduct, and the related terms unadducted material and non-adducted material. While the term adduct is simple and convenient, it is an unfortunate designation, inasmuch as it confuses these complexes with other substances known in the chemical art., Specically, adduct has been applied to Diele-Alder reaction products, formed by reaction of conjugated dioleiins and oleiins and their derivatives.. As is well known, Diels-Alder products, as a rule do not revert to their original constituents when heated or treated with Water, acids, solvents,` etc. Moreover, the term adduct has been dened earlier as The product of areaction between molecules, which occurs in s uch a way that the original molecules or their residues have long axes parallel to one another. (Concise Chemical and Technical Dictionary.) Further ambiguity is introduced by the term adduction, which has been defined as oxidation (Hackh) To avoid the foregoing conflicting terminology,

` several related terms have been coined to deiine with greater specicity `the substances involved in the phenomenon under consideration. As contemplated herein and as used throughoutthe specication and appended claims, the following terms identify the phenomenon:

Plexad-a revertable associated complex compris--V ing a plexor, such as urea, and at least one other compound; said plexad characterized by reverting or decomposing, under the influence of heat and/'or various solvents, to its original constituents, namely, a plexor and at least one plexand.

Plexand-a compound capable of forming a plexad with a plexor, such as urea and thiourea; compounds of this character diier in their capacity to form plexads, depending upon various factors described hereinafter.

Antiplex-a compound incapable of forming a -plexad with a plexor.

Plexor-a compound capable of forming a plexad with a plexand; such as urea andv thiourea.y

Plexate-to form a plexad.

Plexation-the act, process or effect of plexating.

IV. OUTLINE OF INVENTION It has now been found that the separation procedures used hitherto can be improved substantially by the use of certain solvents with a plexor.

As indicated above, urea plexads and thiourea plexads have been formed by contacting a mixture containing a plexand and an antiplex, with urea or thiourea carried in water or an alcohol solution, whereupon a urea or thiourea plexad was formed. The plexad was ,thenA separated from the antiplex by decantation, filtration or similar1 means, and the plexad was decomposed' into its components by heating or by contact with a suitable solvent.

Plexation procedures of the foregoing character, however, are relatively ineicient, inasmuch as an appreciable quantity of an antiplex generally is occluded with the plexad and remains in ad'mixture with the plexand when the plexad is decomposed. This is particularly pronounced in the treatment of lubricating oil stocks, from which waxes are removed by plexation with urea. In addition `to this shortcoming, it has been noted that the waxes so separated from residualtype 'lubricating oilA stocks have considerable color, thus making necessary additional processing to reduce the color of such waxes. A further shortcoming resides in the relatively low degree of' selectivity of aqueous and alcoholic media which carry the urea and thiourea plexors. With such4 media, only relatively small quantities of waxes are removed from lubricating oil stocks. Another important consideration inthe treatment of lubricating oils with urea for removing waxes therefrom is the desirability of a low pour point of the treated oil (antiplex). It has been found that treatment with aqueous and alcoholic media containing urea or thiourea often leads to a treated oilof relatively high pour point.

rThe shortcomings of previous plexation procedures have now been overcome by using mixtures of cresylic acids, particularly mixtures containing substantial amounts of the para isomer, as the urea or thiourea solvent. In some manner, as yet not thoroughly understood, mixtures of cresylic acids cooperate with the plexor to provide a more effective plexation.

V. OBJECTS It is an object of this invention, therefore, to provide an eiective means for separating hydrocarbons and hydrocarbon derivatives of diierent molecular conguration from mixtures containing the same. Y

It is also an object of this invention to separate a rplexad from an antiplex, and to provide a plexand substantially. free of an antiplex. A more particular object is to separate a hydrocarbon Wax from a lubricating oil stock, and to provide a substantially oil-free hydrocarbon Wax characterized by a low degree of color. A corresponding object is theprovision of a lubricating oil substantially free of hydrocarbon wax and/or of appreciably lower pour point than the untreated lubricating oil stock.

Another object of this invention is to separate parafn wax and microcrystalline wax from mixtures thereof. Still another object is to fractionate hydrocarbon waxes from mixtures containing the same.

Another important object is the provision of a continuous method of separation of said plexands and antiplexes, which method is flexible, capable of relatively sharp separation, and not highly demanding of attention and of utilities such as heat, refrigeration, pumping power and the like.

Other objects and advantages of the invention will be apparent from the following description.'

VI. VINVENTION IN DETAIL As indicated above, it has been. found that the foregoing objects are achieved by plexationwith urea or thiourea of a plexand or plexands, the urea or thiourea used being carried in a medium comprising cresylic acid mixtures.

f(1) Pleands and mixtures suitable 'forpleatzojn oxygen-containing mixtures containing straight chain acids, alcohols, a-ld'ehydes, Vesters and/or `ketones having at least six carbon :atoms'per molecule' (Bengen). It will-be apparentfromathe denitions recited above,"that the plexands of y these mixtures are the compounds forming-plexads with urea, and that'the antiplexes `areth'e compounds which do not form urea plexads.

6. in application |Serial No. 116,593, filed Vvconcurrently herewith. Plexation with'ureaof various terminally 'substituted compounds'from mixtures y containing thesame and non-terminally substituted compounds, described in application Serial No. 115,517, led concurrently herewith, is also aided materially by the present process. L

Y Urea plexation of a non-terminallymono-sub- Y stituted compound from mixtures containing the same and-a non-terminally poly-substituted. compound, described in application Serial No. 115,513,

iled 1concurrently` herewith, is 'also'improved' substantially by the present process. Similarly, more effective resolution with-urea of mixtures containing parainic compounds of different degrees of unsaturation is realized herein; these mixtures' are described'in detail inA applicationsjSerial Nos; 115,514 .and 115,518, 'filed concurrently herewith.`

With regard to thiourea plexatiorr the mixtures shown in .applications lSerial Nos.l 115,512

Hydrocarbon mixtures containing n-parains in the range of CF1-Cao andxhigher such as :wax distil1ates,.footsoil, gas oils, virgin ker'osenes,

straight run naphthas are :also suitablel when ureais'used as the plexor, such mixturesbeing shown in copending application `Serial No: 4,997, filed' January 29, 1948. Other mixtures shown in the latter application and 'also' suitablehere are: hydrocarbon mixtures containing n-'para'ins and n-oleiins, andprepared by synthesis of carbon monoxide andthydrocarbons, ire., typical Fischer-Tropsch products prepared using-cobalt and iron catalysts; cracked mixtures prepared by the Vapor phase cracking of stocks rich in nparains, s'uch as by the cracking of parafnic gas oils, foots-oil, crude waxes, etc.; mixtures containing straight chain oxygenated compounds, such as acids, alcohols, aldehydes and esters, and containing branched compounds, such as those obtained by synthesiswith hydrogen and carbon monoxide over an iron catalyst or by oxidation of high molecular weight hydrocarbons; mixtures consisting essentially of n-paraflins and n-olens, for the n-parafns form strongerplexads than the n-olelns; mixtures consisting essentially of n-olens with the double bondY in various positions, for. the olens having the double bond near the end of thechain form stronger plexads than those having'thedouble'bond-further from the end of the chain; hydrocarbon mixtures obtained by isomerization, alkylation, dehydrocyclization, dehydrogenation, etc.

Other mixtures which may be more eiectively plexated with urea by the present process are those containing hydrocarbon derivatives and shown in application Serial No. 115,511, led ooncurrently herewith. Typical of the mixtures'described in the latter application are mixtures containing a straight chain halide having the halogen atomattached to a terminal carbon and having at least aboutl five carbons .in the chain.; 'Mixf nitrogen-containing substituent, arealso advantageously plexated withv the present process; such mixtures include amines, amides, nitriles, nitroparans, etc., and are described in application Serial No.. 115,515, led concurrently herewith,

now abandoned. `Sulfur-containing compoundspresent in various mixtures are also plexated eflciently herein; those are shown in application Serial No. 115,516, i'iled concurrently herewith. Compounds containing cyclic substituents, I present in various mixtures, are also eiciently'plexatedwith urea in thepresent process, being shown tures containing compounds characterized' by Va and 115,730,iledSeptember 13 and'l, respectively, are suitable inthe present process. 'In

application ESerial No.A 115,512, highly branched paraiins and/or highly branched oleflns are separated from straight chain or lless highly' branched compounds: 11n' application Serial No. 115,730, certain cycloparaflins and/or cyclo-olens are separated from mixtures of the same and other hydrocarbons The plexors used herein include urea and thio-` urea and, as indicated aboveftheseplexors are used in solution inc'resylic acidmixtures, particularly'those containing appreciable amounts of p-cresol. This solution should "range fronipartially saturated to supersaturated at the temperature at which it is contacted with a plexand or with a'mixt'ure containing one or more plexands and antiplexes. y In many cases, it will be found convenient tosuspend a further supply of urea or thiourea crystalsin the solution,handling it as a slurry. y As mentioned earlier,mixtures ocresylic acids containing'substantial amounts `of p-cresol are particularly effective, Typical of such mixtures are those used in Duo-Sol refining and customarily referred to as Seleto solvents. The latter comprise mixtures of cresylic acids, or cresols, and contain appreciable amounts of p-cresol. ',Ihe amount 'of p-cresol in vsuch mixtures varies widely, generally from about 5 to about 30 per cent, by weight. Other solvents effective herein comprise mixtures of phenol and cresylic acids, again with material quantities of p-cresol present. Representative of such vmixtures is one .comprisingf 6'0 per cent, b'y'`weightv of-phenol 4.

and-"40 per cent, byweight lof cresylic acids, the

latter containing'f'a'bout'per cent, byweight, ofpf-cresol. 4 Y Y j A 'The solvent used vis substantially inert to the hydrocarbons and/or l'hydrocarbon derivatives underl treatment, and' to urea of thiourea. It

is heat stable, both'alone and in contact withthe hydrocarbons, hydrocarbon derivatives, urea and thiourea, at temperaturesat whichzthe desired 4ple'x'lad is not heat stable. p

Cresyli'cfacid`mixtur`es can'be' used alone orY with another solvent.Y Itis Aoften advantageous and mixtures of cresylic acids.

suitable for use vin "a' multiple-component system, includepsalcoholsfj slycols,1ethers ,aminear acid, acetonitrile, etc.

` tion.

7 polyamines, amides, acids, nitriles, etc. Typical of such solvents are: methanol, ethanol, propanol, ethylene glycol, butylene glycols, ethylene glycol dimethyl ether, triethylamine, hexylamine, piperidine, diaminoethane, diaminopropane, diaminobutane, formamide, formic acid,` acetic Such multiple-component solvents, partially saturated to supersaturated with urea or thiourea, lend themselves readily to a continuous process for separation by plexa- Solutions containing suicient water in order to minimize the solubility of the hydrocarbons or hydrocarbon derivatives in the urea or thiourea solvent are often employed. The minimum quantity of water required depends upon the polarity and thernolecular Weight of the hydrocarbon or hydrocarbon derivative (or plexand) being treated and, in general, this quan'- tity will be greater with more polar plexands and with lower molecular weight compounds.

It is also contemplated herein to include a small quantity of a surface active agent in the urea or thiourea solution, in the manner described in copending application Serial No. 115,437, filed concurrently herewith.

Another modification contemplated herein is the procedure described in copending application Serial No. 137,739, led January 10, 1950, involving contact of hydrocarbons and/or hydrocarbon derivatives with a lplexor impregnated upon a porous support. In this modification, the solvents used with the hydrocarbon and/or hydrocarbon derivatives will be mixtures of cresylic acids as described herein.

An understanding of a preferred embodiment of this invention may be facilitated by reference to the accompanying illustrative drawing, which is a schematic now-diagram of one speciiic arrangement for practicing the invention. In the figure, a mixtureof hydrocarbons such as a waxy oil and a urea-cresylic acid solution,

is introduced through line I to plexation tank 2. The mixture in tank 2 is agitated for a suitable period of time, generally from several minutes to about three hours, at a suitable temperature, for example 125 F., in order to realize a satisfactory degree of plexation. It will be understood that plexation tank 2 is equipped with a suitable stirrer or agitator (not shown). The resulting mixture is taken from tank 2 through line 3, naphtha in line 4 is added to the mixture in line 3, and the composite is introduced into separator 5. Naphtha, such as a fraction boiling at 20D-300 F., is added to-aid in separation of the urea-wax plexad, formed by plexation. and antiplexes of the waxy oil. The sepa-` rator 5 can be a centrifuge, filter, settler equipped with a suitable screw conveyor, etc., as will be understood by those skilled in the art.

Y Antiplex hydrocarbons, or oils, in admixture with some naphtha and cresylic acids are Withdrawn from separator 5 through line 6; and urea- Wax plexad, in admixture with some naphtha and cresylic acids, is withdrawn through line 1.

An additional quantity of naphtha is addedthrough line 8 to the material in line 1, and the resulting material is introduced to a second separator, 9, wherein further classication takes place. In separator 9, antiplex hydrocarbons or oils are removed through line IIJ, and. ureawax plexad, together with some naphtha and cresylic acids, is withdrawn through line II.

The urea-wax plexad, in line II, is contacted with hot water (at about 150 F.) which is addedl through line I2, and passed through heat exchanger I3 to separator I4. The heatexchanger I3 is maintained at about 150 F., such that the urea-wax plexad is decomposed or resolved. Wax is removed from separator I4 through line I5 and is introduced into fractionator I6. Cresylic acids and naphtha removed through line I5 with the wax are taken to storage from fractionator I6 through lines I'I and I8, respectively, and wax is removed from the system through line I9. The wax so recovered can be further treated depending upon the use to which it is to be put.

Cresylic acids recovered in fractionator I6 and Aremoved through line I I are stored in tank 2I,

and can be recycled through line I. Similarly, naphtha taken overhead from fractionator IS throughy line I8 is stored in tank 22, and can be recycled, as through lines 4 and 8.

` From separator I 4, aqueous urea is taken through line 23 to a tower or still 24 wherein urea is concentrated. Water is removed from 24 through line 25, and a concentrated aqueous urea is removed through -line 25 and is taken throughcooler '2l to line I for reuse.

Hydrocarbon oils, antiplexes, in lines Ei and I0, are introducedinto fractionator 28 wherein naphtha and cresylic acids adrnixed therewith are fractionated and are removed through lines 29 and 30, respectively. Recovered cresylic acids and naphtha are stored in tanks 2I and 22, respectively, and can be recycled as indicated above. Hydrocarbon oils, or dewaxed oils, are removed through line 3 I. Y

As shown above, a urea-wax plexad can be decomposed or resolved to urea and Wax, under the influence of water and heat. Plexads, by deiinition, can be so resolved, under the influence of heat and/or certain solvents, such as methanol, ethanol, water and others mentioned above. It is to be understood, however, that urea and thiourea plexads behave differently in various solvents. For example, urea-wax plexads are soluble in isoamyl alcohol and in pyridine at temperatures of about 0-200 F., and do not decompose under such conditions; however, they are recovered from such solvents by evaporation.

VII. ILLUSTRATIVE EXAMPLES The following examples serve to illustrate, and not in anysense limit, the present invention.

A residual lubricating oil stock having the following properties was used vin the illustrative examples:

Pour point, F. 80 SUV 210 F., secs. 75.9 V. I. (approximate) 103 Color, Lovibond (1/4" cell) 115 Gravity, oA. P.I. 28.5 Flash, F. 450

One part ofroil was mixed with 1.9 parts (by Weight) of 'a cresylic acid' mixture and 0.8 part (by weight) of urea at iv F. (52 0.). 'The' resulting mixture was maintained at 12.5 F. for l hour, and naphtha (20G-300 F. boiling range) was added to aid in the separation of plexad and antiplex. The plexad thus formed, comprising hydrocarbon wax and urea, was separated from the mixture by filtration, and the plexad lter cake-was washed with additional naphtha. The plexad was then washed with hot water F.) to decompose the plexad, thereby setting free urea and molten wax. The hydrocarbon plexand, wax, was then separated by decantation. Similarly, the filtrate, or antiplex, was washed withhot water to remove urea therefrom, and naphtha was then removed by distillation. y

Results of this example set forth in the following tabulation.

.lComprises 60 parts, by weight, of phenol; 40 parts, by weight, of cresols (about 35% p-cresol).

Inspection of the foregoing results reveals that a mixture of cresylic acids is an excellent solvent in cooperating with urea to provide an oil of low pour point (45 F.) and to provide a hydrocarbon Wax of high melting point.

The present process has considerable utility in resolving various hydrocarbon mixtures, as illustrated above. As a further example, this process is of value in conjunction with a Duo- Sol rening treat of oil stocks containing asphaltic materials. As is well known, Duo-Sol treats involve the use of a light hydrocarbon, particularly propane, in combination with phenols, generally phenol and cresylic acids, whereupon asphaltic materials are selectively separated from oil stocks. Inasmuch as these oil stocks contain waxes, in addition to asphaltic bodies, it is possible to integrate the present process with a Duo-Sol operation to effect removal of waxes. This is accomplished by a Duo-Sol treat in which a mixture of cresylic acids is used, followed by plexation in the presence of cresylic acid mixture. However, Vthe advantage of integrating these operations resides in the feature of leaving the cresylic acids, in the Duo-Sol treated oil and effecting plexation. By leaving solvent in the raflinate, it is possible to dewax without first removing solvent before the dewaxing operation.

We claim:

1. In the refining of a residual lubricating oil stock containing hydrocarbon Wax wherein said stock is contacted in solution with urea, whereby said hydrocarbon wax preferentially forms a crystalline complex With urea, and wherein said complex and the remaining oil stock are separated, the improvement which comprises: so contacting said oil stock and urea in solution in a mixturev of cresylic acids, at a temperature of about 125 F.

2. In the refining of a residual lubricating oil stock containing hydrocarbon wax wherein said stock is contacted in solution with urea, whereby said hydro-carbon wax preferentially forms a crystalline complex with urea, and wherein said complex and the remaining oil stock are separated, the improvement which comprises: so contacting said oil stock and urea in solution in a phenolic mixture comprising about weight per cent of phenol and about 40 weight per cent of cresols of which about 35 per cent is p-cresol, at a temperature of about F.

3. The process for refining a hydrocarbon oilv stock containing hydrocarbon Wax and asphaltic materials, which comprises: treating said oil stock with a mixture of a light hydrocarbon and a mixture of cresylic acids, whereby an extract rich in asphalti-c materials and a rainate rich in hydrocarbon wax and containing cresylic acids are formed; separating said extract and raffinate; and contacting said raflinate with urea, at a temperature of about 125 F. whereby said hydrocarbon Wax preferentially forms a crystalline complex with urea; and separating said complex and the remaining oil.

OTHER REFERENCES Technical Oil Mission, Reel 143, translation by Shell Development Co., of German patent application B 190,197, IV d 12, May 22, 1946, pages 2-6 only (5 pages). 

1. IN THE REFINING OF A RESIDUAL LUBRICATING OIL STOCK CONTAINING HYDROCARBON WAX WHEREIN SAID STOCK IS CONTACTED IN SOLUTION WITH UREA, WHEREBY SAID HYDROCARBON WAX PREFERENTIALLY FORMS A CRYSTALLINE COMPLEX WITH UREA, AND WHEREIN SAID COMPLEX AND THE REMAINING OIL STOCK ARE SEPARATED, THE IMPROVEMENT WHICH COMPRISES: SO CONTACTING SAID OIL STOCK AND UREA IN SOLUTION IN A MIXTURE OF CRESYLIC ACID, AT A TEMPERATURE OF ABOUT 125* F. 